A system and method is disclosed for simultaneously testing columns and column
redundancies of a semiconductor memory by temporarily adding an additional parallel
signal bit to an input/output data bus associated therewith, the additional parallel
signal bit providing greater bandwidth during test mode operation. The input/output
data bus has n parallel signal bits which normally carry column data, but the additional
parallel signal bit does not normally carry either column data or column redundancy
data. The additional parallel signal bit may normally carry a clock signal such
as an echo clock associated with the data placed on the data bus.
